The present invention relates to a device for maintaining a detonating cord against a transparent aircraft canopy member in order to ensure the cutting out and ejection of the latter.
Numerous pyrotechnic devices exist for the breaking of the aircraft glass and/or transparent material, which permit much faster cutting and evacuation than conventional evacuation or abandonment systems, such as the mechanical release of the canopy.
An example of such pyrotechnic evacuation systems is described in French Pat. No. 2 121 843 which relates to an evacuation system in which the glass is broken by means of a detonating cord placed within an elastomer sheath, itself held against one of the faces of the canopy by a system of support or retaining plates. On the canopy side the sheath is open and the plates must be made from spring steel. Without using an adhesive, they make it possible to maintain the detonating cord against the transparent canopy member, by exerting on the latter a given pressure per unit length of cord and this is independent of temperature variations. These plates must also be provided with saw marks, which are regularly spaced for their arrangement in the cockpit and reinforcing plates are also necessary. The use of spring steel plates is highly disadvantageous from the weight standpoint in the case of cockpits for unpressurized light aircraft. Furthermore, the maintaining of the detonating cord in a flexible sheath, open on the side which bears on the transparent member fails to protect, if the aircraft crashes, the rescuers from projected molten lead and pieces of transparent members projected at high velocities. Finally, in the case of ejection during flight, the sheaths which are no longer maintained in place, may be prejudicial to the movements of the crew and may compromise a rapid abandoning of the aircraft.